Aggression, avoidance, and reaction to novel environments in female rats with ventromedial hypothalamic lesions.

In an experiment with 30 adult female Sprague-Dawley rats, lesions in the ventromedial hypothalamus of 20 Ss (a) increased the probability of pain-elicited aggressive responses; (b) caused a loss of dominance in a situation where fighting was elicited by food competition and territorial defense; (c) did not change interspecies aggressive reactions; (d) facilitated acquisition of avoidance responses in a shuttle box; (e) increased locomotor activity and decreased latency of feeding behaviors in novel environments; and (f) resulted in an increase in locomotor activity in response to the introduction of shock in the shuttle box, in contrast to a decrease seen in controls. (20 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attenuation of gastric lesions by psychological aspects of aggression in rats.

In a study with 80 male albino rats, Ss that fought with each other in response to electric shock showed reduced gastric lesions in comparison with Ss that received the same shocks alone so that fighting behavior did not occur. Also, gastric lesions were similarly reduced in Ss that fought even though they could not physically contact one another because of a barrier between them. In this case, the "protective" effect of fighting derived from the release or display of fighting behavior and did not require physical combat. A 2nd experiment with 48 rats showed that Ss that received shock together but did not engage in fighting behavior showed no reduction of gastric lesions, so that the protective effect of fighting was not an artifact of Ss receiving shock together. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"Attenuation of Gastric Lesions by Psychological Aspects of Aggression in Rats": Erratum.

Reports an error in the original article by Jay M. Weiss, Larissa A. Pohorecky, Sherry Salman, and Michael Gruenthal (Journal of Comparative & Physiological Psychology, 1976[Mar], Vol 90[3], 252-259). The figures on pages 255 and 257 should be reversed as Figure 4 now bears the caption of Figure 3 and vice versa. The figures with their correct captions are provided. (The following abstract of this article originally appeared in record 1976-20292-001.) In a study with 80 male albino rats, Ss that fought with each other in response to electric shock showed reduced gastric lesions in comparison with Ss that received the same shocks alone so that fighting behavior did not occur. Also, gastric lesions were similarly reduced in Ss that fought even though they could not physically contact one another because of a barrier between them. In this case, the "protective" effect of fighting derived from the release or display of fighting behavior and did not require physical combat. A 2nd experiment with 48 rats showed that Ss that received shock together but did not engage in fighting behavior showed no reduction of gastric lesions, so that the protective effect of fighting was not an artifact of Ss receiving shock together. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thyroxine treatment reduces the anorectic effect of estradiol in rats.

Examined a possible interaction between thyroxine and estradiol in the control of feeding in female Sprague-Dawley rats. 14 ovariectomized Ss were given daily injections of 9.8 μg/100 g of body weight of 1-thyroxine (TX). Another 14 Ss received 0.15 ml of saline (SAL) subcutaneously each day, and food intake was measured for both groups daily. After 15 days of treatment, 8 Ss from each group were also given a single injection of 6 μg of estradiol benzoate (EB), and the remaining 6 Ss of each group received peanut oil vehicle. It was found that TX-treated Ss showed a significantly smaller drop in food intake after EB than did SAL-treated Ss. This TX-induced decrease in responsiveness to EB may be related to effects of TX on general metabolism. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decrease in food intake following cortical spreading depression in static obese rats with ventromedial hypothalamic lesions.

Subjected 19 male and 23 female rats with ventromedial hypothalamic (VMH) lesions or with sham lesions to cortical spreading depression (CSD) 150 days after lesioning. Lesioned Ss showed a significantly lower food intake (as percentage of intake before CSD) than sham-lesioned Ss in the 14 days after CSD, but water intake did not differ between lesioned and sham-lesioned Ss. Both groups showed a slight decline in body weight, but lesioned Ss lost significantly more weight than sham-lesioned Ss. After 14 days, body weight, food intake, and water intake had returned to pre-CSD levels in both groups. Findings indicate that Ss with VMH damage are more sensitive to the effects of CSD than are normals and suggest that CSD acts to increase the activity of the VMH and to inhibit food intake, and this increase in activity is prolonged in VMH-lesioned Ss. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A longitudinal study of dominance in an outdoor colony of domestic rats.

A colony of Sprague-Dawley albino rats in a large outdoor enclosure was observed daily for 15 mo. In both the colonizing Ss and their progeny, social dominance followed a 2-stage pattern. Among socially immature males of less than 150 days of age, social interaction typically took the form of play fighting and produced dominance hierarchies that were relatively unstable, nonfunctional in regard to activities such as copulation, and nonpredictive of adult dominance. Socially mature males, in contrast, won contests with aggressive acts such as biting/chasing, had the highest frequencies of social interaction and copulation, and were most active in attacking interlopers. There were also indications, based on more limited evidence, that maternally active females established functional and somewhat stable hierarchies. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related deficits in acquisition of a passive avoidance response.

In Exp. I, 80 male albino rats 10, 15, 20, 30, or 100 days old received a brief inescapable shock contingent upon making a step-off response. Step-off latencies increased for all age groups, but rate of learning was significantly faster in older Ss. Learning appeared to be based primarily upon punishment effects rather than general emotionality, since yoked Ss shocked after being placed directly on the grids did not acquire the avoidance response. Exp. II with 120 Ss employed 3 training conditions with independent groups 12, 15, 18, or 21 days old. The step-off response resulted in shock that was either: (a) escapable; (b) inescapable, 1-sec duration; or (c) inescapable, yoked duration. Younger Ss were again significantly inferior to more mature Ss. Escapable shock improved acquisition at 2 age levels, but the effect appeared to be more related to shock duration than to the response contingency. It is suggested that the requirement of withholding a punished response may represent a category of learning that is especially sensitive to maturational changes. (French summary) (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of dexamethasone on affective behavior and adrenal reactivity following septal lesions in the rat.

Dexamethasone blockade of ACTH secretion from the pituitary gland did not alter the characteristic appearance or duration of the septal syndrome in male Wistar rats observed at 2, 9, and 16 days postoperatively. Despite the lack of a behavioral effect dexamethasone blocked the normal plasma corticosterone response to the stimulus of behavior rating in all groups studied. In the absence of dexamethasone, Ss with a septal lesion had a 65% greater corticosterone level 15 min. following the behavior rating than nonlesion Ss 2 days after surgery and an average increase of 35% over the 3 postoperative observation times of 2, 9, and 16 days. Results provide evidence that, in addition to the adrenal, the pituitary-adrenal axis is not essential for disturbance of affective behavior following septal ablation. (34 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of lesions in the amygdala, periamygdaloid cortex, and stria terminalis on aggressive behaviors in rats.

In 3 experiments, with a total of 113 male albino Sprague-Dawley rats, it was found that small lesions in the periamygdaloid cortex, cortical amygdaloid nucleus, or bed nuclei of the stria terminalis reduced or eliminated attacks and signs of dominance in fights which were generated by isolated housing and the omission of food reward. The same lesions had little or no effect on pain-induced or reflexive "fighting" or on mouse-killing. Small lesions in the lateral or central amygdaloid nuclei significantly inhibited pain-induced "aggression," but did not modify attack behavior or dominance in fights that occurred in situations not involving painful stimulation. These lesions also did not alter mouse-killing behavior. Results suggest that the periamygdaloid cortex and cortical amygdaloid nucleus, as well as the stria terminalis, may be part of a neural system which influences intraspecies aggression in male rats. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food wrenching and dodging: A neuroethological test of cortical and dopaminergic contributions to sensorimotor behavior in the rat.

Sensorimotor behavior in unilateral decorticate and unilateral dopamine-depleted rats was studied in a naturally occurring social interaction in which rats compete for food with relatively stereotyped species-typical responses. In the interaction a "robber" attempts to wrest food from a feeding "victim," which in turn protects the food by making rapid contralateral dodges. Hemidecortication abolished dodging to food wrenching attempts made by a rat approaching contralaterally to the lesion, so that the food was stolen, but recovery occurred between 15 and 60 days after surgery. Use of the side contralateral to the lesion to wrest food was moderately impaired, and recovery of food wresting was more rapid than recovery of dodging. Unilateral dopamine depletion produced dodging impairments to food-wresting attempts that were made both ipsilateral and contralateral to the side of the lesion, and the deficits endured over 60 test days. The food was frequently lost to food-wrenching attempts made contralateral to the lesion, whereas the direction of dodges to approaches ipsilateral to the lesion was reversed. Food wresting was also bilaterally impaired. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex and social play in juvenile rats (Rattus norvegicus).

Four experiments were conducted to examine the effects of pretest social isolation, sex of the social stimulus, and test cage familiarity on sex differences in play fighting in 156 juvenile Long-Evans rats. Reliable sex differences were found only when Ss were tested after 6 days of isolation in undisturbed cages (Exp III). In contrast to weak sex effects, pretest isolation and test cage familiarity were robust variables influencing levels of play fighting in juveniles of both sexes. Results are discussed in reference to procedural differences among experimental approaches that have examined sex differences in social play. It is suggested that social investigatory behavior and play behavior appear to be reciprocally related. Hence, the sex difference in social play is accompanied by an apparent reversal in the sex effect seen with social investigation. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of prefrontal cortex ablation in neonatal, juvenile, and young adult rats.

Long-Evans hooded rats sustaining lesions in the medial (MF) or the orbital (OF) prefrontal cortex at various ages (10, 25, 40, or 60 days postnatally) were tested as adults on a series of behavioral tasks that are known to be sensitive to such lesions in adults. On spatial alternation learning, both the 40- and 60-day MF Ss were seriously impaired, whereas neither the 10- nor the 25-day MF Ss differed from controls. On a hoarding task, 25- and 60-day MF Ss hoarded less food than either controls or 10-day MF Ss. Lesions of OF cortex in males at 40 or 60 days significantly increased running-wheel activity; OF lesions in both sexes at 25 days of age or later decreased the rate of continuous reinforcement reacquisition relative to controls, whereas 10-day OF Ss did not differ from controls on either task. Thus, Ss with lesions of either frontal area at 10 days of age showed complete behavioral sparing on all measures. The effects of lesions at later ages varied with the behavioral task employed and with lesion locus. Although the 10-day Ss received a somewhat longer postoperative recovery interval than most of the later operates, these results cannot be explained on the basis of recovery time alone. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learned helplessness and immunization: Sensitivity to response–reinforcer independence in immunized rats.

Exps I and II, with 62 male Holtzman rats, examined the learned helplessness and immunization effects using a test in which appetitive responding was extinguished by delivering noncontingent reinforcers. Contrary to learned helplessness theory, "immunized" Ss showed performance virtually identical to that of Ss exposed only to inescapable shock and different from that of nonshock controls. Exp II suggested that the helplessness effect and the lack of immunization were not due to direct response suppression resulting from shock. In Exp III, in which the immunization effect was assessed in 28 Ss by measuring the acquisition of a response to obtain food when there was a positive response–reinforcer contingency, immunization was observed. Results cannot be explained on the basis of proactive interference and instead suggest that Ss exposed to the immunization procedure acquired an expectancy of response–reinforcer independence during inescapable shock. Thus, immunization effects may reflect the differential expression of expectancies rather than their differential acquisition as learned helplessness theory postulates. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of olfactory bulbectomy on social behavior of male guinea pigs ( Cavia porcellus ).

Studied the effects of olfactory bulbectomy on social behavior in 16 male guinea pigs. Both brief exposure pairing techniques and a group-living observation period were employed to test for disruption. During short-term testing sessions bulbectomized Ss courted females less than but mounted them as frequently as controls. While the groups did not differ in fighting behavior during short-term tests, controls scent-marked more frequently. Subsequently, Ss were observed as same-treatment pairs living continuously with females, and behavior was sampled over a 3-wk period. Under these conditions bulbectomized males, unlike controls, failed to form dominance orders, exhibited virtually no intermale aggressive activity, had markedly depressed sexual activity, and scent-marked rarely. It is concluded that olfactory bulbectomy profoundly alters the behavior of male domestic guinea pigs and that those alterations are most evident when experimental Ss are observed in a species-typical group-living environment. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Competitive fighting in the rat.

Obtained competitive fighting in 29 of 60 pairs of like-sexed DA agouti laboratory rats by placing a single piece of food into the food hopper following 48 hrs of food deprivation. The fighting was characterized by offensive sideways posture, full aggressive posture, and bite and kick attack. Tests were conducted at 110-120 days of age on pairs of Ss that had been housed together since weaning. Fighting was more frequent in pairs consisting of nonlittermates than in pairs of littermates, and it was equally frequent in male and female pairings. Probability of fighting was enhanced by prior experience with food deprivation, and attack was most often initiated by the heavier animal of the pair. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioned suppression of humoral immunity in the rat.

180 Charles River rats were conditioned by pairing consumption of a novel sodium saccharin drinking solution with the effects of an ip injection of 75 mg/kg cyclophosphamide, an immunosuppressive drug. Five and 10 days after conditioning, an experimental group (Group CS) was reexposed to the saccharin drinking solution. Control Ss (Group CSo) were conditioned but were not reexposed to saccharin. On Days 10, 15, or 25 after conditioning, Ss were injected ip with sheep erythrocytes, and independent subgroups were sampled for hemagglutinating antibody titer 4, 6, or 8 days later. Antibody titers 4 days after immunization were lower than values observed 6 and 8 days after immunization, and CS Ss had an attenuated antibody response. There were no significant differences between Group CSo and a group of placebo-treated Ss, but CS Ss had lower antibody titers than placebo-treated animals 4, 6, and 8 days after antigenic stimulation. Results suggest that reexposure to a CS may have long-lasting effects, and provide further documentation of conditioned immunopharmacologic effects and the impact of behavioral factors in modifying immunologic reactivity. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food-motivated behavior in rats with cortico-basomedial amygdala damage.

In 6 experiments, 12 male Wistar rats with cortico-basomedial amygdala damage (CBM) and 20 sham-operated controls were tested in several food-related situations. The CBM Ss showed a longer latency to eat than controls in a novel environment due to more pronounced exploration. In the competition for food, CBM Ss lost 85% of encounters with controls. Immediately after the contest, when allowed to eat singly, CBM Ss displayed a higher persistence of alimentary responses to an emptied cup than did controls, presumably because they experienced more losses in the food competition. Both groups were equally able to overcome obstacles on the way to food, which suggested similar alimentary motivation. The only direct indication of a lowered responsiveness to hunger in CBM Ss was 24-hr fasting-induced hypophagia. Results indicate the involvement of the cortico-basomedial amygdaloid region in the control of relations between alimentary and other motivations. The contribution of eventual changes of food motivation in the postoperative alteration of this balance is discussed. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of androgen on marking and aggressive behavior of neonatally and prepubertally bulbectomized and castrated male gerbils.

Exp I assessed the role of olfactory and androgenic influences on the development of scent-marking and aggressive behavior of 69 male gerbils. Ss were bilaterally bulbectomized, unilaterally bulbectomized, castrated, given a combination of bulbectomy and castration, or given a sham operation at 2 days of age. Marking and fighting were recorded prior to and after androgen treatment in adulthood. Postoperative tests revealed that neonatal olfactory bulb removal, alone or in combination with castration, virtually eliminated scent-marking and fighting. Treatment with testosterone propionate (TP) in adulthood was ineffective in facilitating marking after neonatal castration, bulbectomy, or their combination. However, Ss given TP did exhibit increased aggressiveness. The most striking increases were found in bulbectomized and bulbectomized-castrated Ss. In Exp II (117 Ss), bulbectomy, castration, or their combination at 35 days of age also reduced both marking and fighting. Androgen treatment in adulthood did, however, fully restore marking in all groups to control levels with the exception of bulbectomized-castrated Ss. Fighting was increased to extremely high levels following TP treatment in bulbectomized and bulbectomized-castrated Ss. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Increased feeding by rats after subdiabetogenic streptozotocin treatment: A role for insulin in satiety.

80 adult male Sprague-Dawley albino rats given streptozocin (streptozotocin) showed varying degrees of glucose intolerance, ranging from mild to overt symptoms of diabetes mellitus. After being deprived of food overnight, both mildly and overtly diabetic Ss consumed more food than 47 controls during 5- or 7-hr feeding tests. All Ss ate large amounts of food during the 1st hr of the tests, but both groups of diabetics began to eat again sooner than controls did. Ss demonstrating the greatest degree of glucose intolerance before the test ate the most during the test. Findings suggest that feeding by diabetic rats after an overnight fast is an inverse function of their residual capacity for glucose utilization, which occurs despite elevations in blood glucose levels, and is not simply a compensatory response to glucose loss in urine. A modified glucostatic hypothesis is proposed in which insulin may normally promote satiety by influencing peripheral metabolism and making ingested calories usable. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivational and neuroanatomical specificity of hypodipsia for aversive solutions produced by medial preoptic injury to the rat.

In an experiment with a total of 28 Sprague-Dawley rats, bilateral medial preoptic lesions dramatically lowered the rejection threshold for quinine-adulterated water but not for food in 24-hr forced-choice tests. The detection threshold for quinine in a 2-bottle choice test, however, was unaffected by the medial preoptic lesion. Bilateral septal and lateral preoptic lesions had no effect on any quinine adulteration tests. The enhanced rejection of quinine-adulterated water in a forced-choice test by medial-preoptic-damaged Ss was also observed after 24 hrs of water deprivation. The plasma osmolality of medial preoptic Ss was significantly elevated above controls after 24 hrs of water deprivation. Findings suggest that a medial preoptic lesion produces a deficit in thirst-motivated behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)